Let me test the most common one first: (A ↔ Z, B ↔ Y, etc.).
It looks like you've provided a phrase that appears to be encoded with a (like Caesar cipher) or an atbash cipher . thmyl mtsfh upx mhkr
Try (Caesar shift +3): t → w h → k m → p y → b l → o → "wkpbo" no. Let me test the most common one first:
"thmyl" t-1 = s h-1 = g m-1 = l y-1 = x l-1 = k → "sglxk" no. B ↔ Y